Fogged direct positive silver halide emulsion containing a cyanine dye having a 2-aliphatic,chlorine,or hydrogen-substituted indole nucleus

ABSTRACT

DIRECT POSITIVE SILVER HALIDE EMULSIONS WHICH CONTAIN AT LEAST ONE DIMETHINECYANINE DYES IN WHICH THE 3-POSITION OFTHE INDOLE NUCLEUS HAVING A HYDROGEN ATOMS, CHLORINE ATOM, LOWER ALKYL GROUP, CARBOXYL GROUP OR LOWER ALKOXYCARBONYL GROUP IN THE 2-POSITION THEREOF JOINS TO THE 1-, 2-, 3- OR 4-POSITION OF THE CYANINE HETEROCYCLIC NUCLEOUS THROUGH A DIMETHINE CHAIN, WITH THE PROVISO THAT ONLY WHEN THE CYANINE NUCLEUS IS ISOQUINOLINE IS THE JOINING TO THE 1- OR 3-POSITION, AND WHEN JOINING IS TO THE 4-POSITION, THE CYANINE NUCLEUS COMPRISES A QUINOLINE OR PYRIDINE RING.

PatentQf 3,832,184 FOGGED DIRECT POSHTIVE SILVER HALIDE EMULSION CONTAINING A CYANINE DYE .1 HAVING A Z-ALIPHATIC, CHLORHQE, R HY- DROGEN-SUBSTITUTED INDOLE NUCLEUS Akira Sato, Tadashi Ikeda, Akira Ogawa, Keisuke hiba, A and Masanao Hinata, Kanagawa, Japan, assignors to Fuji Photo'Film Co., Ltd., Kanagawa, Japan a No Drawing. Filed Dec. 26, 1972, Ser. No. 318,047 Claims priority, application Japan, Dec. 24, 1971,

Int. Cl. G03c 1/08, 1/28, 1/36 U.S. Cl. 96--101 20 Claims AESTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the Invention Thej present invention relates to silver halide emulsions, more specifically to direct positive silver halide emulsions sensitized by novel dimethinecyanine dyes.

Description of the Prior Art In the case that a silver halide photosensitive material is exposed to light which includes rays having a wave length to which the photosensitive material is sensitive and then developed, photographic density increases as exposure increases and reaches a maximum value, whereafter photographic density decreases with further increase of the exposure. This phenomenon is generally called solarization. i Further, in silver halide photosensitive materials which are optically or chemically fogged during the production thereof, a reversal phenomenon the same as in the case caused by light (the phenomenon that the photographic density decreases with increased exposure) is observed. It is possible to'produce positive images utilizing such a phenomenon.

The direct positive silver halide emulsions in the present specification are silver halide emulsions which are prepared so as to form positive images directly upon exposure to light (positive light image) and developing.

H As s ensitizersifor common negative emulsions, many dyes, for example, monomethinecyanines, trirnethinecyanines, merocyanines and rhodanines are known. However, when these dyes are used for sensitization of direct positive silver halide emulsions they sometimes cause many faults, for example, softening of the characteristic curve (flattening) and re-reversal (the photographic densi'ty increases again after decrease thereof with increased exposure 4 1 Further, many dyes known as sensitizers are direct positive silver halide emulsions have the fault that they cause residual color in the photosensitive materials after treatmen't. Such residual color is disadvantageous in photographic'printing paper because when such dyes are used as the sensitizer it is impossible to obtain high whiteness in monochromatic photographic printing paper and it is impossible to carry out true color reproduction in the v 3,832,184 Patented Aug. 2?, 1974 SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide direct positive silver halide emulsions which retain maximum image density and do not cause residual color.

The present invention relates to direct positive silver halide emulsions which contain at least one dimethinecyanine dye in which the 3-position of the indole nucleus (which has a hydrogen atom, chlorine atom, lower (C -C alkyl group, carboxyl group or lower (C -C alkoxycarbonyl group in the 2-position thereof) joins to the l, 2, 3 or 4-position of the cyanine heterocyclic nucleus, with the proviso that only when the cyanine heterocyclic nucleus is isoquinoline is the joining to the 1- or 3- position (but when joined to the 4-position, the cyanine nucleus is a quinoline or pyridine), through a dimethine chain, and, if desired, an organic desensitizer.

DETAILED DESCRIPTION OF THE INVENTION As examples of the substituent in the 2-position of the indole nucleus of dimethinecyanine dyes used in the present invention there are a methyl group, ethyl group or butyl group as the lower alkyl group and a methoxycarbonyl group, ethoxycarbonyl group or t-butoxycarbonyl group as the lower alkoxycarbonyl group.

As examples of the cyanine heterocyclic nucleus of the dimethine cyanine dyes used in the present invention, there are, for example, an oxazoline nucleus, oxazole nucleus, benzoxazole nucleus, naphthoxazole nucleus, thiazoline nucleus, thiazole nucleus, benzothiazole nucleus, naphthothiazole nucleus, selenazole nucleus, benzoselenazole nucleus, naphthoselenazole nucleus, Z-pyridine nucleus, 4-pyridine nucleus, 2-quinoline nucleus, 4-quinoline nucleus, 3-isoquinoline nucleus, l-isoquinoline nucleus, benzoimidazole nucleus, 3,3-dialkylindolenine nucleus, e.g., 3,3-dimethylimidazo-(4,5-b)-quinoxaline nucleus and pyrrolidine nucleus, wherein the heterocyclic nucleus may have substituents. As examples of Such substituents there are alkyl groups, aryl groups, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a nitro group or ahalogen atom, with preferred alkyl groups having 1-20 carbon atoms, preferred alkoxy groups having l-lO carbon atoms and a preferred aryl group being a phenyl group. As examples of such cyanine nuclei, there are, for example, thiazoles such as thiazole, 4-methylthiazole, 4-phenylthiazole, 4-(p-hydroxyphenyl)thiazole, S-methylthiazole, S-phenylthiazole, 5-(o-hydroxyphenyl)- thiazole, 4,5-dimethylthiazole and 4,5-diphenylthiaz'ole'; benzothiazoles such as benzothiazole, 4-hydroxybenzothiazole, 4-fiuorobenzothiazole, 4-chlorobenzothiazole,' 5 chlorobenzothiazole, 6 chlorobenzothiazole, 7 chloro benzothiazole, 4 methylbenzothiazole, 5 methylbenzothiazole, 6-methylbenzothiazole, 5,6 dimethylbenzothiazole, S-brornobenzothiazole, 6-brornobenzothia zole, 5- phenylbenzothiazole, 6 phenylbenzothiazole, 4 phenylbenzothiazole, 4-meth'oxybenzothiazole, 5-methoxybenzdthiazole, 6-methoxybenzothiazole, 7-methoxybenzothiazole, S-iodobenzothiazole, 6-iodobenzothiazole, 5 etlioxy benzothiazole, 4-ethoxybenzothiazole, fi-ethoxycarbonylbenzothiazole, tetrahydrobenzothiazole, 5-(N,N-dimethyl'- amido)benzothiazole, 5,6-dimethoxybenzothiazole', S-hydroxybenzothiazole, 6 hydroxybenzothiazole, 5 nitrobenzothiazole and 5-chloro-6-nitrobenzothiazole; naphthothiazoles such as a-naphthothiazole, B-naphthothiazole, fl,B-naphthothiazole, 8-methoxy 13 naphthothiazole, ethoxy-B-naphthothiazole, 7-rnethoxya-naphthothiazole, 8-methoxy-a-naphthothiazole, 5 hydroxy-fi-naphthothiazole, 7-hydroxy-a-naphthothiazole and S-ethyl-fl-naphthothiazole; oxazoles such as oxazole, 4-methyloxazole, 5- methyloxazole, 5 phenyloxazole, 4 (p-hydroxyphenyl) oxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole, 4-phenyloxazole, and 5-(m-hydroxyphenyl)- oxazole; benzoxazoles such as benzoxazole, S-chlorobenzoxazole, S-methylbenzoxazole, 5-phenylbenzoxazole, 6-methylbenzoxazole, 6-nitrobenzoxazole, 5,6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, S-methoxybenzoxazole, 5 ethoxybenzoxazole, 6 chlorobenzoxazole, -methoxybenzoxazole, 5-hydroxybenzoxazole and 6-hydroxybenzoxazole; naphthoxazoles such as u-naphthoxazole, 8,;8-naphthoxazole, B-naphthoxazole and 6-hydroxy-fi-naphthoxazole; selenazoles such as selenazole, 4- methylselenazole, 4-phenylselenazole and 4-(p-hydroxyphenyl)selenazole; benzoselenazoles such as benzoselenazole; S-chlorobenzoselenazole, 5-methoxybenzoselenazole, S-hYdroxybenzoselenazole and tetrahydroxybenzoselenazole; naphthoselenazoles such as a-naphthoselenazole, ,8,}3-naphthoselenazole, B-naphthoselenazole and 7-hydroxy-;3-naphthoselenazole; thiazolines such as thiazoline, 4-methylthiazoline, and 4-(p-hydroxyphenyl)thiazoline; 2-quinolines such as quinoline, 3-methylquinoline, 5- methylquinoline, 7-methylquinoline, S-methylquinoline, 6-chloroquinoline, 8-chloroquinoline, 8-fluoroquinoline, 6-methoxyquinoline, 6-ethoxyquinoline, 6-hydroxyquinoline, 7-hydroxyquinoline and S-hydroxyquinoline; 4-quinolines such as quinoline, S-methoxyquinoline, 6-methoxyquinoline, 7-methoxyquinoline, 8.-methoxyquinoline, 6- methylquinoline, 7-chloroquinoline and 8-trifiuoromethylquinoline; isoquinolines such as isoquinoline, S-methyl-lisoquinoline, 7-methyl-l-isoquinoline, 6-chloro-1-isoquinoline, 6-methoxy-1-isoquinoline and S-methoxy-l-isoquinoline; 6 chloro-3-isoquinoline, 6-methoxy-3-isoquinoline and 8-methoxy-3-isoquinone; 3,3-dialkylindolenines such as 3,3-dimethylindolenine, 5-hydroxy-3,3-dimethylindolenine, 3,3-dimethyl-6-chloroindolenine, 3,3,5 trimethylindolenine and 3,3-dimethyl-S-nitroindolenine; Z-pyridines such as pyridine, 6-methylpyridine, 4,6-dimethylpyridine, 4-butylpyridine, 4-decylpyridine, 4-octadecylpyridine, 4,6- dibutylpyridine, 4-benzylpyridine, 4-phenylpyridine, 4-(phydroxyphenyl)pyridine, 4,6 diphenylpyridine, 4,6 dinaphthylpyridine, 4-chloropyridine, 4-bromopyridine, 4,6- dichloropyridine, 4-chloropyridine, 6-bromopyridine, 4- hydroxypyridine, 4-methoxypyridine, 4-ethoxypyridine, 6-methoxypyridine, 6-ethoxypyridine and 4,6-dimethoxypyridine; pyridines such as pyridine, 2-butylpyridine, 2- methylpyridine, 2-butylpyridine, 2-decylpyridine, 2-octadecylpyridine, 2,6-dibutylpyridine, 2-benzylpyridine, 2- phenylpyridine, Z-(p-hydroxyphenyl) pyridine, 2,6-diphenylpyridine, 2-chloropyridine, 2-brornopyridine, 2,6-dichloropyridine, Z-hydroxypyridine, 2-methoxy pyridine, 2-ethoxypyridine and 2,6-dimethoxypyridine; imidazo- (4,5-b)quinoxalines such as 1,3-diethylimidazo-(4,5-b)- quinoxaline, 1,3 diethyl 6 nitro-imidazo-(4,5-b)-quinoxaline, 1,3 diphenylimidazo (4,5-b) quinoxaline, 6-chloro 1,3 diphenylimidazo (4,5-b) quinoxaline, 1,3-diallylimidazo (4,5-b) quinoxaline and 1,3-dicyclohexylimidazo-(4,5-b)-quinoxaline; oxazoline and benzimidazoles such as benzimiclazole, 5,6-dichlorobenzimidazole, 1-ethyl-5-nitrobenzimidazole and 1-ethyl-5,6-dichlorobenzimidazole.

The dimethinecyanine dyes used in the present invention can be synthesized, for example, by reacting aldehyde derivatives of indole compounds having a hydrogen atom, chlorine atom, lower alkyl group, carboxyl group or lower alkoxycarbonyl group in the 2-position with alkyl substituted quaternary ammonium salts of compounds having the desired cyanine heterocyclic nucleus in a suitable solvent, such as acetic anhydride and nitrobenzene, by heating. Other processes which may be used are taught in US. Pats. 3,431,111 and 3,632,808.

4 The alkyl substituted quaternary ammonium salts of compounds having the desired cyanine heterocyclic nucleus can be represented by the formula:

where, for example, A is methyl, substituted methyl, e.g., methoxymethyl, etc. A methine chain may be formed by joining the carbon atom of the methyl group of A and R The other symbols have the same meaning as in Formula I.

Preferable dimethinecyanine dyes used in the present invention are represented by the following formula (I).

In the formula, R represents a hydrogen atom or nitro group, R represents a hydrogen atom, chlorine atom, lower (C -C alkyl group, carboxyl group or lower (C -C alkoxycarbonyl group, R represents a hydrogen atom, alkyl group having 1-6 carbon atoms or aryl group such as phenyl or substituted phenyl such as tolyl, methoxyphenyl and nitrophenyl, R represents an alkyl group having 1-6 carbon atoms, allyl group or aryl group such as phenyl or substituted phenyl, L represents an unsubstituted methine group, L represents methine group, e.g., a methine group which can be lower alkyl (C -C substituted, aralkyl substituted, e.g., benzyl, aryl substituted, e.g., phenyl, etc., substituted, wherein a substituent in L may bind to R to form a methylene chain, m and n each represent 1 or 2, X- represents an anion, and Z represent the non-metallic atoms necessary to complete a cyanine heterocyclic nucleus.

In formula (I), R and Z were described in detail in the above. Examples of the alkyl group having 1-6 carbon atoms in R include a methyl group, ethyl group, butyl group or hexyl group, which may be substituted, for example, with a carboxy group. As the aryl group in R a phenyl group and a tolyl group are particularly preferable. Examples of the alkyl group having 1-6 carbon atoms in R include, for example, a methyl group, ethyl group, propyl group, hexyl group, a hydroxyalkyl group (e.g., a fi-hydroxyethyl group), alkoxyalkyl groups (e.g., a ,s-methoxyethyl group), carboxyalkyl groups (e.g., ficarboxypropyl group), sulfoalkyl groups (e.g., a 'y-sulfopropyl group) and aralkyl groups (e.g., a monocyclic aralkyl group, preferably, having less than 3 carbon atoms in the alkyl moiety such as a phenethyl group and a henzyl group). As examples of the aryl group in R a phenyl group and a tolyl group are particularly preferred. With respect to L the substituent in the substituted methine group may be, for example, a methyl group, ethyl group, carboxyethyl group, phenethyl group, hydroxyethyl group, a methoxyethyl group, and this substituent may bind to R to form a methylene group. In this case, it is particularly preferred to form a 5- or 6-member ring.

As examples of X-, there are, for example, a chlorine ion, bromine ion, iodine ion, p-toluenesulfonic acid ion, ethylsulfonic acid ion and a perchlorate ion. n is 1 in the case that the compound represented by the formula (I) has a betaine structure or 2 in the other cases.

In the following, particularly preferred examples of the compounds represented by the formula (I) are de scribed, wherein the maximum absorption wave length in a methanol solution of the compound (AMeOH max.

is shown.

TABLECon tinued 1s o H MeOH 432 nm.

I z 5 max. Ton-:cn-

-oooo2H5 f i C2H5 9 CH3 CH3- -s 03 17 AEZXOIH 481 Hm.

CH=CH l l es omen 2 T;/\/ 3 f (0 93 3 on.

1 S MeOH 468 nm.

8 max.

QH=CH sg coon -o 00 0.11 l \N/ 02H. omQ-sm 19 S\ wMnggH 473 um.

11-01;:011- a; o 0 00H c o 0 0211 N/\/ C2H5 om-Q-sme on,

20 so MeOH 478 nm.

max. N0. CH=CH U l /--CH3 I N 0 11 6 CH3 I S MeOH 482 nm. 21"" max.

CH=CH-\ H e l N ornornonon; toe

In the following, examples of the synthesis of various sensitizers are described.

SYNTHESIS l 1 2 (2 (1 methyl 2 ethoxycarbonyl 3 indolyl) vinyl) 1,3 diethylimidazo(4,5 b)quinoxalium ptoluenesulfonate Dye (2) 1.0 g. of 1-methyl-2-ethoxycarbonyl-3-formylindole and 1.82 g. of Z-methyl-1,3-diethylimidazo(4,5-b)quinoxaliump-toluenesulfonate were added to 20 ml. of acetic anhydride. After refluxing for minutes by boiling, the solution was cooled with ice water whereby crystals precipitated. After adding about 200 ml. of ethyl alcohol thereto, the crystals were separated by filtration and washed with a solvent mixture of ethyl ether and acetone. The crystals were then recrystallized from a solvent mixture of ethanol and methanol. Thus, 1.6 g. (yield; 59 wt. percent based on starting materials; hereafter all dye yields are on the same basis) of Dye (2) (m.p.: 207 C.) was obtained.

SYNTHESIS 2 2- (2-( 1-ethyl-2-chloro-3-indolyl vinyl) l-ethylbenzoxazolium iodide Dye (9) 2.1 g. of 2-methyl-l-ethylbenzoxazolium iodide and 1.5 g. of 1-ethyl-2-chloro-3-formylindole were added to ml. of acetic anhydride. After refluxing for about 10 minutes by heating, the mixture was treated in the same manner as in Synthesis 1. By crystallizing from a solvent mixture of ethanol and methanol, 1.2 g. (yield: 35%) of Dye (9) (m.p.: 230 C.) was obtained.

Other dirnethinecyanine dyes can be synthesized in a manner similar to those described by merely substituting appropriate starting materials. The synthesis procedure per se is conventional.

It is further preferred that an organic desensitizer be included in the direct positive emulsions of the present invention.

The organic desensitizers used in the present invention aer substances which have the ability to trap free electrons generated in silver halide particles by the application of radiant rays, and are substances which are adsorbed in the silver halide particles. Preferably, they are compounds having a maximum occupied electron energy level lower than that of the valence electron zone of the particles. Measurement of the values of the electron energy levels can be made, though complicated operations are necessary. For example, determination for simple symmetric cyanine dyes is described in Photographic Science and Engineering, Vol. 11(3), page 129 1967), Tani and Kikuchi. Another such deterrnination for typical merocyanine dyes is described in Preprint (No. B-12) of International Congress of Photographic Science, 1970 (Moscow), Shiba and Kubodera.

It is known that the electron enregy level corresponds primarily to an anode polarographic half-wave potential (Eox) and a cathode polarographic half-wave potential (Ered). Many of such organic desensitizers are described in, for example, US. Pats. 3,023,102, 3,314,796, 2,901,351 and 3,367,779, in British Pats. 723,019, 698,575, 698,576, 834,839, 667,206, 748,681, 796,873, 875,887, 905,237, 907,367 and 940,152, French Pats. 1,520,824, 1,518,094, 1,518,095, 1,520,819, 1,520,823, 1,520,821 and 1,523,626, Belgian Pats. 722,457 and 722,594, and Japanese Patent Publication No. Sho 4313,167 and No. 4314,500.

Any desensitizer described above can be used in the present invention. However desensitizers which give a particularly preferred result are compounds represented by formula (II) in which the cathode polarographic halfwave potential (Ered) is more positive than 1.0 volt.

In formula (II), R represents an alkyl group or allyl group, Z, X- and m each have the same meaning as in formula (I) and a represents 1 or 2.

Specific examples of R include a methyl group, ethyl group, butyl .group, hydroxyalkyl groups (e.g., an hydroxyethyl group), carboxyalkyl groups (e.g., a carboxymethyl group and a 3-carboxylpropyl group) and sulfoalkyl groups (e.g., a 2-sulfoethyl group and a 4-sulfobutyl p).

Other organic desensitizers used in the present invention with success include, for example,

phenosafranine,

pinakryptol yellow,

S-m-nitrobenzylidene rhodanine,

3-ethyl-S-m-nitrobenzylidene rhodanine,

3-ethyl-5-(2,4-dinitrobenzylidene)rhodanine,

5-o-nitrobenzylidene-3-phenyl rhodanine,

1,3-diethyl-6-nitrothia-2'-cyanine iodide,

4-nitro-6-chlorobenzotriazole,

3,3'-diethyl-6,6-dinitro-9-phenyl-thiacarbocyanine iodide,

2-(p-dimethylaminophenyliminomethyl)benzothiazole ethoethyl sulfate,

Crystal Violet,

3,3-diethyl-6,6'dinitro-thiacarbocyanine ethyl sulfate,

l,3-diethyl-6-nitrothia-2'-cyanine iodide,

1,3-diamino-S-methylphenazium chloride,

4-nitro-6-chlorobenzotriazole,

3,3-di-p-nitrobenzylthiacarbocyanine bromide,

3,3'-di-p-nitrophenylthiacarbocyanine iodide,

3,3-di-onitrophenylthiacarbocyanine perchlorate,

3,3'-dimethyl-9-trifiuoromethylthiacarbocyanine iodide,

9-(2,4-dinitrophenylmercapto)-3,3'-diethylthiacarbocyanine iodide,

bis-(4,6-diphenylpyryl-2-trimethine cyanine perchlorate,

anhydrous 2-p-dimethylaminophenyl-iminomethyl-6-nitro- 3-(4-sulfobutyl)benzothiazolium hydroxide,

l- Z-benzothiazolyl -2- (p-dimethylaminostyryl -4,6-

diphenylpyridinium iodide,

1,3-diethyl-5-( 1 ,3-neopentylene-6- 1,3 ,3-trimethyl-2- indolinylidene -2,4-hcxadienylidene -2-thiobarbituric acid,

2,3,5-triphenyl-ZH-tetrazolium chloride,

2- (4-iodophenyl -3- (4-nitrophenyl) -5-phenyl-tetrazolium chloride,

1-methyl-8-nitroquinolinium methyl sulfate, and

3 ,6-bis- (4- 3-ethyl-2-benzothiazolinylidene -2-butenylidene)-1,2,4,5-cyclohexanetetrone.

As examples of the silver halide emulsions used in the presentinvention, there are silver chloride, silver bromide, silver bromochloride, silver iodochloride and silver iodobromochloride.

Though the silver halide may have a particle size in the range of those as are commonly used in this art, those having an average particle size of 0.05it-L0 give a particularly preferred result. The silver halide used in the present invention may be composed of either regular particles or irregular particles, but regular particles display a more prefered effect. (See US. Pat. 3,501,306.)

While either monodispersed emulsions or non-monodispersed emulsions may be used in the present invention, monodispersed emulsions are preferably used. (See U.S. Pat. 3,501,306.)

In general, raw emulsions used in direct positive silver halide photosensitve materials are classified into two types.

In one type the emulsion has nuclei for trapping free electrons in the interior of the silver halide crystals, the surface of which has previsuoly been chemically fogged. A characteristic of emulsions of this type is that they di rectly form positive images themselves, and it is possible only not to increase a spectral sensitization function but to sensitize the intrinsic absorption region of such emulsions by adding sensitizing dye(s) thereto. In emulsions of this type the compositions of the silver halides present should be adjusted so that chemical sensitizers or metal salts of a Group VIII metal which are used to give free electron trapping nuclei easily enter into the interior of the silver halide.

Further, by addition of the organic desensitizer, it is possible to decrease minimum density (clean out) and particularly to prevent re-reversal. Furthermore, it is possible to increase the maximum density, sensitization and to improvement clean-out by adding bromine ions in an amount of from 1 to 10 mol percent or iodine ions in an amount of from 0.2 to 3 mol percent based on the silver halide.

The emulsion of this type is described in US. Pats. Nos. 2,401,051, 2,717,833, 2,976,149 and 3,023,102, British Pats. Nos. 707,704, 1,097,999 and 1,520,822, and French Nos. 1,523,626, 1,520,817 and 1,520,824.

The second type of raw emulsions used in forming direct positives are those which do not have free electron trapping nuclei in the interior of the silver halide but wherein the surface is chemically fogged. These emulsions are silver halide emulsions composed of regular crystals which do not have a twinning plane and which are as free of lattice defects as possible. Such emulsions are preferably pure silver bromide. These emulsions do not form direct positive images themselves. However, if they adsorb organic desensitizer in the silver halide of the emulsons, direct positive images are obtained at high sensitivity.

The emulsion of this type is described in US. Pats. Nos. 3,501,306, 3,501,307, 3,501,310 and 3,531,288, British Pats. Nos. 1,186,717, 1,186,714 and 1,186,716 and French Pats. Nos. 1,520,821, 1,520,817, 1,522,354 and 1,520,824.

In the present invention, either of the above raw emulsions can be used, i.e., both raw emulsions can be effectively sensitized by adding the compounds in accordance with the present invention, preferably those represented by formula (I).

The silver halide emulsions used in the present inven tion can be fogged by light or chemically. Chemical fog nuclei can be formed by adding, for example, hydrazine derivatives, formalin, thiourea dioxide, polyamine compounds, amine borane, methtyldichlorosilane and other known agents as disclosed in Belgian Pats. Nos. 721,564 and 708,563, US. Pat. No. 2,588,982, British Pat. Nd. 821,251, French Pat. No. 739,755 and Japanese Patent Publication No. 43-13,488. r

Further, fog nuclei can be formed by using a reducer together with metal ions nobler than silver (for example, gold ions, platinum ions and iridium ions) or further with halogen ions, as disclosed in US. Pats. Nos. 2,717,833 and 3,023,102, Belgian Pats. Nos. 713,272 and 721,567 and British Pat. No. 707,704. W

In the emulsions used in. the present invention, gelatin is usually used as the protective colloid, and inactive gelatin (inert gelatin) is preferably used. Instead of gelatin, however, photographically inactive gelatin deriva: tives and water soluble synthetic polymers (for example, polyvinyl acrylate, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl alginate, carboxymethyl cellulose and by droxyrnethyl cellulose) can be used, alone or as mixtures.

The direct positive silver halide emulsions used in the present invention may containv additives such as a fog nuclei stabilizers (e.g. mercapto compounds, thione compounds and tetrazaindene compounds), an agent to decrease minimum density (e.g. stilbene compounds and triazine compounds), a whitening agent, an ultraviolet ray absorbing agent, a hardener (e.g. chromium alum, 2,4- dichloro-s-triazine compounds, azilydine compounds, epoxy compounds, mucohalogen acids and halogenoformyl-maleic acid derivatives), a coating assistant (e.g. sodium polyalkylene sulfonate, saponin and anionic surface active agents having a betaine structure), an antiseptic, a plasticizer (e.g. polyalkylacrylate, alkylacrylateacrylic acid copolymers and polyalkylene oxide) and a color coupler.

The amount of the dimethine dyes used in the present invention depends upon largely on the quantity of silver halide and the surface area of the silver halide particles, but 1 10- to 2x10 mols per mole of solver salt provides good results.

These dyes are applied by dissolving them in water or water miscible solvents such as methanol, ethanol, ethylene glycol monomethyl ether, methylethylketone, acetone and pyridine. Ultraonic vibrations can be applied to the dyes during dissolution, if desired. Further, the methods used in the sensitization of negative type emulsions, for example, as described in Japanese Patent Publication No. Sho 44-23389, Sho 44-27,555 and Sho 44-22,948, U.S. Pats. 3,485,634, 3,342,605 and 2,912,343, or German Pat. 1,947,935 can also be used. The addition of the dyes to the emulsion is conveniently carried out just before applica- 5 tion to the support, but the dyes may be added during chemical ripening or at precipitation of the emulsion.

An amount of the organic desensitizer used in the present invention varies depending upon the kind thereof, but 2 10' mols per mol of the silver halide(s) is preferably used.

The emulsions according to the present invention can be applied to many kinds of supports to produce photographic elements. The emulsions may be applied to one surface or both surfaces of the support. The support may be transparent or opaque. As typical supports there are cellulose nitrate films, cellulose acetate films, polyvinyl acetal films, polystyrene films, polyethylene terephthalate films and other polyester films, glass, paper, metal, wood,

etc. Plastic coated paper can also be used.

After exposure to light, the emulsions according to this invention are preferably treated in a development bath, a fixing bath and a stabilizing bath or in a bath which combines all of these treatments.

' One characteristic of the present invention is to sensitize direct positive emulsions using certain new dimethine dyes which do not cause substantial residual color. A chemical structural feature of the new dimethine dyes is that the 2- position of the indole nucleus is substituted by a hydrogen atom, lower alkyl group, chlorine atom, carboxyl group or lower alkoxycarbonyl group.

It is described in U.S. Pat. 2,323,187 that sensitizing dyes which have a sensitizing function for common negative emulsions, particularly carbocyanine dyes,are effective for the sensitization of direct positive emulsions if they are used in a very large amount. However, this method'is not prefered since the dyes strongly color the emulsions and cause residual color. On the other hand, it is described in British Pats. 970,621 and 1,186,714 that dimethine' dyes having a 2-phenylindole nucleus or 2-pyridylindole nucleus show an excellent reversal property. However, they are unsatisfactory because residual color is caused. In the case of adding such dyes to direct positive emulsions untilmaximum sensitivity is obtained, a particular'tendency for residual color to occur is encountered.

The dimethine dyes discovered by the present inventors have the characteristic that the residual color is very low, with residual color hardly being observed in the case that the 2-position of the indole nucleus is substituted by a "carboxyl group or a lower alkoxycarbonyl group;

The second characteristic of the present invention is that the maximum density of the direct positive emulsion does not decrease substantially upon theuse of the dyes of the present invention.

Not only carbocyanine dyes and merocyanine dyes which are useful for sensitization of negative emulsions but dimethine dyes having a 2-phenylindole nucleus sometimes cause deterioration of the maximum density of direct positive emulsions. Decrease of the maximum density is caused not only just after application of the direct positive photographic emulsions but also during storage of the emulsions. This deterioration of the direct positive photosensitive materials with the lapse of time is larger than that of common negative photosensitive materials. Accordingly, the improvement of this point is an important subject. The new dimethine dyes used in the present invention have excellent properties in this respect.

The third characteristic of the present invention is that not only do the dimethine dyes used in the present invention cause a low degree of residual color but also flattening of the characteristic curve (softening) is small. In general, carbocyanine dyes and merocyanine dyes which are useful for the sensitization of negative emulsions have a tendency to flatten the characteristic curve. This flattening of the characteristic curve is not preferred in a high contrast direct positive sensitive materials such as reproduction films for lithotype films.

The direct positive silver halide emulsions sensitized by the dimethine dyes used in the present invention have a good clean-out (minimum density) and have the excellent characteristic that re-reversal does not substantially occur.

As mentioned above, the new dimethine dyes used in the present invention have many excellent characteristics. However, if these dyes are used together with the organic a desensitizer, reversal sensitivity further increases and it is possible to produce direct positive silver halide emulsions having good clean-out.

The direct positive silver halide emulsions according to the present invention can be used not only for hard direct positive silver halide photosensitive materials such as photosensitive materials for the reproduction of lithotype films and photosensitive materials for copying originals, but also for comparatively soft direct positive silver halide sensitive materials such as photosensitive materials for the reproduction of microfilm and photosensitive materials for the reproduction of X-ray films, etc. Further, they can be used for color photosensitive materials.

The direct positive silver halide emulsions according to the present invention are useful not only in the case of application of light but also in the case of application of electrons X-rays and 'y-rays, etc.

The present invention will now be illustrated in greater detail by several examples. In the examples, the dyes used for comparison purposes were as follows:

..=.H W as CH=CH [Q CHzCHzCHa Q cut-Gs 01 era-@sm l CzHi @omcmcmooon Br CHzCHzO CH;

C H=C e/ N N I a CzHs N as M) Q N EXAMPLE 1 In order to prepare a raw emulsion, Solutions 1-4 were prepared according to the following formulations:

Solution 2 and Solution 3 were slowly added to Solution 1 over minutes while keeping all solutions at C. The mixture was then subjected to physical ripening at 60 C. for 5 minutes. Then, 15 cc. of a 0.2N solution of potassium iodide was added thereto and the pAg was adjusted to 6.0 by adding silver nitrate solution thereto. After adjusting the pH to 10 with a sodium hydroxide solution, the solution was subjected to ripening for 10 minutes by adding 1.2 mg. hydrazine and 1.0 mg. of potassium tetrachloroaurate (III) thereto. The solution was then neutralized with citric acid and washed with water. Solution 4 was added thereto to prepare a raw emulsion. The resulting emulsion contained silver halide particles having an average particle size of about 0.2 comprised particles of a regular tetragonal system having a phase.

To this raw emulsion, dyes were added in accordance with the formulations shown in Table l and 40 mL/kg. of emulsion of as 4 wt. percent aqueous solution of saponin was added. The resulting emulsions were applied to cellulose triacetate films so as to be about 5a in dry film thickness to thereby produce samples. Each sample was exposed for 1 second through a light wedge with a light source of 2854 K. (tungsten light). Then the samples were developed at 20 C. for 2 minutes using the following developer and fixed in an acid hardening fixer. By measurement of the density of the samples with a P-type densitometer produced by Fuji Photo Film Co., Ltd, the characteristic curves of the samples were obtained. Results of measurement of the sensitivity,the maximum optical density (D and the minimum optical density (D of each sample are shown in Tablel.

In Table 1, the sensitivity is shownby. the inverse number of the exposure necessary to give a concentration of and is the value based on the sensitivity of each comparison dye being set at 100.

Composition of the developer: G. Metol 3.1 Anhydrous sodium sulfite 45 Hydroquinone 12 Sodium carbonate monohydrate 79 Potassium bromide 2 Water to make 1 liter. 7

This is used by diluting 1:1 with water.

TABLE 1 Dye (molar concentration) Sensicc./l g. of emulsion tivity D n. min.

Sample number: I v

' 1 (1 (sxlo- 10 138 3.2 0.05

(A) (8X10-B) 16 100 2.0 0.08

2- (2 (sxros 105 3.0 0.04. (B) (8x10 s 100 2.5 0.04

3 (a) (sx10) s 123 3.1 0.04 o axles 100 2.8 0.04

4 (6) (8X10-") 's 120 3.0 0.05 (F) 1 8x10 s 100 2.6 0.05

(7) (8X10-2) 32 410 3.2 0.19 (G) (sxio- 32 100 2.5 0.26

0 (10) (axle- 32 110 2.9 0.04 (J) (8X10-) 32 100 2.2 0.04

-It will be understood from Table 1 that the dyes of the present invention have excellent characteristics in that D is high, the clean-out is good and the sensitivity is high as compared with the comparison dyes.

EXAMPLE 2 First, a raw emulsion was prepared as follows.

To Solution 1 (prepared by dissolving 10 g. of inactive gelatin in 5 cc. of a 1N sodium chloride solution and 500 cc. of water at 60 0.), Solution 2 (prepared by dissolving 100 g. of silver nitrate in 500 cc. of water at 60 C.) and Solution 3 (prepared by dissolving 35 g. of sodium chloride in 300 cc. of water at 60 C.) were added over minutes while stirring at 60 C. After addition, the mixture was subjected to ripening for 5 minutes at 60 C. Then, Solution 4 (prepared by dissolving 14 g. of potassium bromide in 200 cc. of Water at 60 C.) was added over 5 minutes with stirring. After ripening for 10 minutes at 60 C., the temperature was reduced to 35 C. and the product was washed with water. It was then dissolved by warming, and the pH was adjusted to 10. After adding hydrazine and the gold chloride in the amounts given in Example 1, the mixture was subjected to ripening for 10 minutes. Then the pH was adjusted to 6.5 with 8 ml. of 10 wt. percent citric acid. Furthermore, Solution 5 (prepared by dissolving 75 g. of inert gelatin in 300 cc. of water) was added thereto to produce a raw emulsion. The average particle size of silver halide particles in the resulting raw emulsion was about 0.15 1.

To this raw emulsion, 32 cc. of a methanol solution of pinnacryptol yellow (5 10- moles present) was added.

-- Then dyes were added in accordance with Table 2. After adding mucochloric acid and saponin (as in Example 1), the emulsions were applied to cellulose triacetate films so as to have dry film thickness of about 2p. to'fthercby produce samples.

1 ET i 'n hyqrfeqs sodium sums--- -g.. 30 Paraformaldeh'yde g 7.5 I Sodium bisulfate g 2.2 i s-" sid". 1-5 Hydroquiiioiie 22.5 Potassium bromide g 1.6

Water to make 1 liter.

By density determinations using a P-type desitometer produced by Fuji Photo Film Co., Ltd., characteristic curves'of the samples were obtained. In the same manner as in Example 1, the sensitivity, D and D were determined. The density of the residual color was also determined, the density of residual color being shown as the optical density as determined by the above-described densitometer using a blue filter after dipping the emulsion coated samples immediately in an acid hardening fixenat 20 C. for a minute and 30 seconds without exposure to light, and rinsing for 3 minutes. The results are shown in Table 2.

TABLE 2 Dye (molar concen- Residtratlon) cc.ll00 Sensiual g. 01 emulsion tivity Du D i color Sample No 7 (4) (2.5X10- 8 467 3.2 0.06 0.04 (D) (2.5X10'") 8 100 3. 0 0. 07 0. 10

8 (5) (2.5X10- 16 155 2.5 0.04 0.02 (E) (2.5X10' 10 100 2. 4 0. 04 0. 05

9 (8) (2.5X10- 8 107 2.9 0.04 0.01 (H) (2.5X10' 8 100 2.5 0.04 0.04

:10 (9) (2.5X10) 8 104 2.7 0.04 0.01 (I) (2.5X10") v 8 100 2.6 0.04 0.03

11 (l3) (2.5Xl0") 32 118 2.9 0.04 0.05 (K) (2.5x10- 32 100 2.6 0.04 0.17

12 (21) (2.5X10- 16 152 3.0 0.04 0.01 (L) (2.5X10' 16 100 2. 8 0. 04 0. 03

As is clear form this table, the dyes, of the present invention have excellent properties with respect to sensitivi'ty, maximum optical density and cleanout, and the residual color is low. It is surprising that this difference is based on the difference of the substituent in the 2-position of the indolenine nucleus.

EXAMPLE 3 First, a raw emulsion was prepared as follows.

To Solution 1 (prepared by dissolving 10 g. of inactive gelatin in 5 cc. of 1N sodium chloride solution and 500 cc. of water at 0.), Solution 2 (prepared by dissolving 100 g. of silver nitrate in 500 cc. of water at 60 C.) and Solution 3 (prepared by dissolving 35 g. of sodium' chloride and 14 g. of potassium bromide in 300 cc. of water at 60 C.) were added over 20 minutes while stirring at 60 C. After addition, the mixture was subjected to ripening for- 5 minutes as in' Example 2, and the temperature was reduced to 35 C. After washing with water. the mixture was dissolved again by warming and the pH'was adjusted to 10. After adding hydrazine and gold chloride as in Example: 2, the'mixture was subjected to' iripenin'g for 10 minutes, at 60 C. and the pH was adjusted to'6. 5 with citric acid as in Example 2.

FurthermoreQSolution 5 (prepared by dissolving "g. of ifiactivfgfelatin in 300g, of water)"was added thereto to produce a rawemulsion. The average particle lsion, 32 a methanol solution of pinna'cryp'tol yellow (5')(10' m'oles present) was added.

adding mucochloric' acidjandj'saponin' as 2), the emulsionsfwere' applied'to c'e nlos tria cet'a te films so as to have dry filmfthicknes's o about [1. to

thereby produce two strips. One' of t'h'e st'r'ips waspreserved at 35 C. and 75% relative humidity fon'30 days I and exposed to light in the same manneras in Example 1. The-other strip was exposed to light just aftena-p'plication and drying. These samples were developed, fixed and rinsed with water. The density of the-resulting; strips was;-

determined with a P-type densitometer producedby Fuji Photo-Film Co., Ltd. Theresults are shown" in :Table 3.

As is clear from Table 3, the lowering of the maximum optical density (D with the passage of time is small for the dyes of the present invention as compared with the comparison dyes.

The most preferred embodiments of the-present invention can be described as follows.

(1) Where the dimethine cyanine dyes are compounds represented by formula (I).

(2) Where the R group of the dimethinecyanine dyes represented by formula (I) is a hydrogen atom, chlorine atom, carboxyl group or lower alkoxycarbonyl group.

(3) Where the organic desensitizer is a compound represented by formula (II):

wherein R represents an alkyl group, X- represents an anion, m and a each represent 1 or 2, and Z represents the non-metallic atoms necessary to complete a 5- or 6- membered heterocyclic ring.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

1. Fogged direct positive silver halide emulsions which contain at least one dimethinecyanine dye in which the 3-position of the indole nucleus, having a hydrogen atom, chlorine atom, lower alkyl group, carboxyl group or lower alkoxycarbonyl group in the 2-position thereof, joins to the 1-, 2-, 3-, or 4-position of the cyanine heterocyclic nucleus through a dimethine chain, with the proviso that only when the cyanine nucleus is isoquinoline is the joining to the 1- or S-position, and when joining is to the 4- position, the cyanine nucleus comprises a quinoline or pyridine ring, said dimethinecyanine dye; being-present in an amount eifective to provide maximum retained image density without residual color.

2. The direct positive emulsions of- Claiml-wherein the cyanine nucleus is selected from the-.group-consisting of an. oxazoline nucleus, oxazolenucleus, benzoxazole nucleus, naphthoxazole nucleus, thiazoline :nu'cleus, thiazole nucleus, benzothiazole nucleus, naphthothiazole nucleus, selenazole nucleus, benzoselenazole nucleus,-naphthoselenagole nucleus, Z-pyridine nucleus,. 4=pyridine nucleus, 2- qumoline nucleus, 4-quinolinenucleus, .3-isoquinoline nu cleus, 1 -isoquinoline nucleus,- benzoimidazole nucleus," 3,3- dialkylindolenine nucleus, imidazo(4,5-b)quinoxaline 'nucleus and pyrrolidine nucleus.

3. The direct positive emulsions-of Claim 2 wherein the cyannme nucleus is substituted with one or more members selected from'the group consisting of an alkyl group, an

aryl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoiry carbonyl group, 'a nitro group or s hal.

ogen atom.

4. The direct positive emulsions of Claim 1 wherein said "dimethinecyanine dyes are represented by the formula:

hydrogen atom, C -C alkyl group, carboxyl group or C C alkoxycarbonyl group, R is a hydrogen atom or C C alkyl group, R comprises a C C alkyl group, an allyl group or an aryl group, L and L comprise a methine group, in and n are 1 or 2, X- is an anion, and Z represents the non-metallic atoms necessary to complete a cyanine heterocyclic nucleus.

5. The direct positive emulsions of Claim 4 wherein L is a substituted methine group, wherein thesubstitu tent is selected from the group consisting of alkyl, alkoxyalkyl aralkyl or aryl.

6. The direct positive emulsions of Claim 4 wherein R is phenyl or tolyl, R is hydroxyalkyl, alkoxyalkyl, carboxyalkyl, sulfoalkyl or aralkyl with 1 to 6 carbon atoms in the alkyl chain, and R is phenyl or tolyl.

7. The direct positive emulsions of Claim 1 which further include an organic desensitizer, which organic desensitizer has a cathodic polarographic half-wave potential (Ered) more positive than 1.0.

8. The direct positive emulsions of Claim 7 wherein said organic desensitizer has a cathodic polarographic half-wave potential (Ered) more positive than 1.0 and has the formula:

wherein R is an alkyl group or allyl group, X- is an anion, m and a are 1 or 2 and Z represents the non-metallic atoms necessary to complete a cyanine heterocyclic nucleus.

9. The direct positive emulsions of Claim 7 wherein from 2x10 to 10- moles of organic desensitizer is present per mole of silver halide present.

10. The direct positive emulsions of Claim 8 wherein R is an alkyl group and Z represents the non-metallic atoms necessary to complete a 5- or 6-membered heterocyclic rmg.

11. The direct positive emulsions of Claim 1 wherein from 1X 10- to 2x 10- moles of dimethine dye per mole of silver halide is present.

12. The direct positive emulsions of Claim 1 wherein the 2-position of said indole nucleus is substituted with a hydrogen atom.

13. The direct positive emulsions of Claim 1 wherein the 2-position of said indole nucleus is substituted with a chlorine atom.

- 14. The direct positive emulsions of Claim 1 wherein the 2-position of said indole nucleus is substituted with a lower alkyl group.

wthe 2-.position of said indole nucleus is substituted with a carboxyl group.

17. The direct positive emulsions of Claim 1 wherein the 2-position of said indole nucleus is substituted with a lower alkoxycarbonyl group. I

2-1;? 22' 18. The direct positive emulsions of Claim 17 wherein 19. The direct positive emulsions of Claim 4 wherein said lower alkoxycarbonyl group has from 1 to 4 carbon said dimethinecyanine dye is selected from the group conatoms. sisting of:

1.5:: cm on, l oli 522n1n.

No: CH CH- \e f COOCIH! (CH,)ISO' f 7 CH:

aim: 02H geOH 467 nm.

8!. /N CH CH ea v 000cm. g

8....:: S 3 911 466mm.

N0 cH=cH CHa Jz l 4J3: MeOH 512 nm.

max. 7

l c'H'=cH-\$ N/ N CH;

JJHI

Se 1 -l--l'l- N gggH 48911111.

CH=CH- H HzCHaCH] 6. ':l.; I CH2CH=CHi 442111.11.

TABLE-Continued is..." 02m gi g n 432mm.

N N02 (EZH N 000mm 17 MeOH 481 nm.

S max. CH=CH- I I \ea coNwHm H 2): 0x N/ 18..-" S ggy-H 468 nm.

CH=CH I NO CH=CH- g I l Ni 6 H: or

21.; s 153?]?! 482 mu.-

CH=CH I \e l :I I E HaCHaCHCHa H N/ A019 20. A direct positive photographic material which com- 0 3,314,796 4/1967 Gotze et a1 96-130 prises a support having coated thereon the fogged direct 3,713,832 1/1973 Shiba et a1. 96101 positive emulsion of Claim 1.

References Cited UNITED STATES PATENTS 65 RONALD H. SMITH, Primary Examiner 3,505,070 4/1970 Litzerman et a1. 96130 W H LOUIE IR. Assistant Examiner US. Cl. X.R. 

